Portable rechargeable battery packs are used to power portable devices, particularly portable devices that are in frequent use and use a significant amount of power. For example, portable communication devices, such as cellular phones and portable two-way radios are typically left on so as to be able to receive communications at any time while in use. Such constant power consumption makes the use of primary battery cells (e.g. non-rechargeable) uneconomical, and in such cases the use of rechargeable battery cells is much more cost efficient.
Many portable rechargeable battery packs are designed to be charged while attached to a device powered by the portable rechargeable battery pack, as well as alone (not attached to a device). Accordingly, it is conventional for a portable rechargeable battery pack to have two sets of contacts: a set for providing power to the host device, and a set for charging the portable rechargeable battery pack while the portable rechargeable battery pack is attached to the host device. The set of contacts used to charge the portable rechargeable battery pack can be referred to as the charging contact set, or simply referred to as charging contacts. Charging contacts can be exposed while the portable rechargeable battery pack is attached to a host device, which can expose them to undesirable conditions, such as short circuiting across the positive and negative charging contacts.
To address the issue of exposed charging contacts, portable rechargeable battery packs are typically provided with a charge protection means in the portable rechargeable battery pack that prevents electric current from discharging through the charging contacts, while also being operable to allow a charging current when the portable rechargeable battery pack is being recharged. For example, it is common to place a diode in series between the positive charging contact and the rechargeable battery cell(s) inside the portable rechargeable battery pack to allow charging current into the portable rechargeable battery pack and block current from discharging through the charging contacts.
There has been a continuing demand for portable devices, and hence the need for portable power. Accessories and other devices are presently available which do not need a conventional AC to DC adapter, but do not have their own power source. For example, there are a number of devices that can be powered from a computer, such as a laptop computer, via a universal serial bus (USB) of the computer. Unfortunately, because of the charge protection circuit typically used in such battery packs, the battery packs cannot be used to power accessory devices from the charging contacts.
Accordingly, there is a need for portable rechargeable battery pack, system, and external adapter that allows powering of devices through the charging contacts but without significantly compromising the safety of charge protection at the charging contacts of a portable rechargeable battery pack.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.